Hives breakout. Still breaking out HELP?

its been getting warmer and warmer and i never had any allergies. That i know of. i Just turned 15 this month and yesterday i vwent out to the park there were bearly any trees out and it wasnt even that windy. after i walked to my cousins house and then i took a nap on her bed(with my clothes still on). I woke up and discover hives breaking out on my back. Now shes very very clean and i dont have a alergy to any sheets or blankets. so i wasnt sure why i got it. then later on that night they gotten worse spread to my legs and arms and swollen up there on my neck. big red swollen welts the size of quarters. I put on two medications to help and they didnt do anything(benedryl and another cream). Im so lost and confused. I NEED HELP THEY ICTH!!..P.S the foods i ate that day were cookies i eaten before and i drank a soda iv'e drank before to so i dont think its food.